Found an old (80s?) watch that might be very nice if suitably revived.

Any advice on...
- where to source a crystal that's plain and round and slim and flat and c.22mm?
- who to ask to polish / re-plate it?
- whether to get the quartz movement serviced or just whip a new cell in and hope for the best?

Try Cousins UK for the crystal. Replating can be very expensive so I'm not sure it would be worth it on a watch like this. Google gold plating and email a few companies for a quote.

Try a new battery first but if it doesn't work then it will need a service which again will be quite expensive. Most quartz watches aren't serviced, the movement is just exchanged for a new or refurbished one. You could carry out this exchange yourself with some basic tools as the movements are generally less than £20 to purchase.

Thanks Raul
I will go down the new battery route and hope it runs well enough for occasional use at least.
Good advice. I shall seek some quotes for replating and if too much just polish it up a bit.

Now. The crystal.
I can see I can get a sapphire crystal for about £9 from Cousins - which is brilliant - but how do I fit it?

I've never done anything remotely like that before. Is there a tutorial anywhere on this marvellous RLT WF or do I have to resort to listening to some zit-covered teenage geek from Oklahoma telling me what to do on YouTube?! ;-(

The usual tool for this job is a crystal puller. This has a circle of fine teeth and a screw thread which compresses the teeth evenly and gently enough to very slightly compress the crystal just enough to allow it to be removed from the case. Fitting a new crystal is the reverse, the new one is compressed enough to allow it to fit (just enough and no more) and then "un-compressed" into position as a friction fit.

Sometimes a crystal may also be cemented into place. A sapphire crystal is a bit OTT for a Gucci fashion watch IMO (never humble) but each to his own.

Sounds a bit advanced for me - I stop short at changing batteries and refurbishing acrylic crystals at the moment!

The battery change alone looks like it's going to be quite a task as there's a lot of old battery leakage/corrosion.

Can anyone advise on the best cleaning solvent for this job?

At least if I could get it clean inside and the cell changed and the watch going again, I can then feel it's perfectly justified to spend £25 getting the local jeweller to fit a new crystal. Better than the £100 he's quoted for cleaning it out!